I'm sure a decent percentage is innate, but to the trained eye what ingredients would make for a fluid easy mover? I weigh 150-155 lbs and should be moving much easier but I don't, I'm a heavy stepper especially considering my lightweight. I could live without being quick but the heavy stepping is taking it's toll on my lower body. Plus the last heavy step into my shot makes my recovery or transition to the next shot a little worse. I noticed people who constantly on their toes and have played soccer are much easier movers, the other factors I don't know.

Unless you engage lower back muscles, your 155 lbs will put too much pressure on just a few leg muscles, especially if you try to be on your toes all the time. With proper posture and stance/balance, the tension will be more evenly distributed across all the leg muscles.